I have a column in a dataframe, chr and in the form "%Y-%m-%d %H:%M:%S". I have no problem converting them to POSIXct. However, if I leave that column as chr and after I use group_by with that column as the first column of the new dataframe, I cannot convert that first column to POSIXct any more
R says do not know how to convert 'abc[, 1]' to class “POSIXct”. I check the structure of the new dataframe and the first column is still chr. Really appreciate any help.